Question: some help with antennas for DTV

scandiskwindows9x

Moderator of DTV Latino
#1
Well i am wondering and asking for some help about rooftop antennas, i do not know what antenna choose, are in the market many rooftop antennas but i do notn know which one is the more appropiated for DTV, i have tried with an RCA ant 121 Rabbit Ear and the reception of DTV is a disaster, just pixellation and breaks, well i know the system that we use in Chile is very different than the ATSC system that uses Mexico, Canada, USA and others countries, but well, i need some help.

Some ideas of what antenna can be the best to me or how locate the antenna, my house is two story one maybe 4 or 4.5 meters height 15 feets.

Well, any ideas would be appreciated, by the way have tried amplifiers of signal of 10 DB, just not happened anything.

Greetings,

Francisco
 
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MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#2
Francisco,
Yea, I don't have much faith in indoor antennas myself. The only ones that have worked well for me are outdoor antennas mounted indoors, and away from the TV, like a 2-bay. The ISDB-T Japanese standard Chile has adopted is different from the US system, but that won't affect your antenna choices. What matters is what channels are they broadcasting on - VHF lo/hi, UHF?

We'll need to know what VHF and UHF frequencies they're broadcasting there in Chile. I'm assuming that your UHF channels go higher than 51, would that be correct?

I'm sure you won't have the same choices there without shipping from overseas, but we could make some suggestions and you can find something similar. OR, if your channels are all UHF and VHF hi, you could build a 2 or 4 bay antenna.

But definately, get your antenna outside for best results. You're pretty close to the towers. You may have a little problem with multi-path, but I see nothing to prevent you from getting good OTA signals.
 
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n2rj

Moderator
Staff member
#3
The biggest difference between 8VSB and COFDM is the effect of multipath. I believe that with COFDM, multipath actually enhances the signal, unlike with 8VSB where it deteriorates it.

So I guess that means in your case that you are suffering more from signal attenuation than you are multipath. So probably even the most basic outdoor antenna would make a huge difference in your case.
 

scandiskwindows9x

Moderator of DTV Latino
#4
Well made an antenna from myself an logarithm one of 8 elements or bars plus a reflector and works mostly ok, now have not much pixellation , i saw in an chilean website how to do an antenna that works and well i did it and works ok , that mean that need an logarithm antenna and not an normal rooftop on, well the rare is that the antenna now is in my house indoor and works, just have lost one channel.

here is the channel list

the frequency spacing is by 143 MHZ separation, i have tried setting in japan the box and the spacing is of 140MHZ the spacing in Japan.

Signal Frequency Channel City
Canal 13 533143 KHZ Canal 24 Santiago
CHV (chilevision) 569143 KHZ Canal 30 Santiago
TVN 587143 KHZ Canal 33 Santiago
MEGA 551143 KHZ Canal 27 Santiago
La RED 557143 KHZ Canal 28 Santiago

well the canal 13 have two signals the canal 13C that is in SD and the main channel that is HD and some programms and commercials upscaled.

the Chilevision have 2 signals the CHV 1 that is the main channel the CHV 2 that plays music of people that i do not know or heard of them in my life, that channel broadcast in the CHV1 11MB in Full HD and the CHV 2 3MB Full HD the bitrates .


have lost the channel 28

the only frequency channel that can not be used in the system that have choosed is the channel 37 i do not know the technical reasons for that.

OFDM is not that resistant to multipath as many people thinks, all is according with how many carriers you use for broadcast. is many modes, also OFDM is not resistant to impulsive electric noise caused by motors. just have two corrections errors systems that is Viterbi coder and FEC (Foward Error Correction).

in COFDM Multipath made signal fading and can get no signal at all when you have lost all the carriers by multipath effect, in fact in my house if put the indoor antenna get no signal and not matter where i locate the antenna. the result is the same no signal. so COFDM do not do any good work with multipath situation like a indoor location.

the difference with 8VSB is that have a pilot signal where is the "street" where the data is send , with COFDM we just trust that the thousand carriers sent any of those be picked by the antenna.if any of those is not picked, lost the channel for complete. also COFDM have an disadvantage in places with thick walls have problems to penetrate that material and get to the antenna, that is my case in my house the bricks are of brick and very thick ones.





the COFDM have modes of broadcast too in the mode 2K offer 2048 carriers to be send to the radioelectric space, any of those can be caught by an antenna, in the mode 8K offer 8.192 carriers in the radioelectric space. those are COFDM broadcast modes, i do not know what mode are using in here i tend to think are using 2K mode.
 

MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#5
It appears that all your signals are in the what we would consider the UHF band, so a 2 or 4 bay would work pretty good up on the roof, or even in an attic. Try something like this:



Eagle Aspen Dtv2Buhf Directv 2-Bay Uhf Antenna


There's a lot like this out there, look around.
Search Amazon for uhf antenna


You should be able to find something similar in Chile,
or BUILD ONE:
project1_sky.jpg

I built this in an afternoon for just a few dollars.
 
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FOX TV

Contributor
#6
The biggest difference between 8VSB and COFDM is the effect of multipath. I believe that with COFDM, multipath actually enhances the signal, unlike with 8VSB where it deteriorates it.

So I guess that means in your case that you are suffering more from signal attenuation than you are multipath. So probably even the most basic outdoor antenna would make a huge difference in your case.
You are right about COFDM being more robust in dealing with multipath. That was one of the biggest fears of using 8-VSB, and the predictions were very accurate at the time. They had a fit with 8-VSB reception in the earliest days of initial testing because of multipath.
 

FOX TV

Contributor
#7
Mr. Pogi, have you attempted to build a version of the clear stream C-2 or C-4? I built one and it works very well hanging in my Kitchen over the sink on a planter bar i put up between two cabinets over the sink, and it does a good job, even without the backplane reflector. The one I built for outdoor use does have the backplane reflector, and it does as well as the commercial version with a re-designed feed assembly (Balun) as the original design.

Luckily, the station has a commercial version that I could test and compare my home brew version with, and it is on par with the store bought antenna, although the balun design is different than factory. They use a built in balun and have a 75ohm f type connector built in from the factory. One less chance for water ingress into the cable or balun itself. I really like these antennas, and especially in this mountainous terrain in my area.

The tapered element design makes it fairly broadband, but it is a little weak up in the high end of the uhf band.
 
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scandiskwindows9x

Moderator of DTV Latino
#9
well is a store in the downtown Santiago that only they sales antennas and that type of things, maybe one of those days go to see what have they avalaible, was thinking in use an WI fi Antenna for receive DTV, is this one

PC Factory • Tu centro tecnológico • Antena.24.dBi.Grillada.ANGR2424.Wireless

or was thinking in something more discreet like that (well Casa Royal is our specie of RadioShark) in fact RadioShark was here till the year 2002 when they decided left the country.
http://www.casaroyal.cl/productos.aspx

well is this one

WALITO TV antenna

but i do not know i do not have much fait in the antenna that look like an cell phone ministation , because the gain is of 6Db is the same than the antenna that comes with my converter Box

this antenna comes with the converter Box
Taiwan DVB-T Antenna. Lu-Chu Trading Company, Manufacturer, Exporter, Consultant

i just do not had much faith to that and well not worked at all

well here is the link of the store that mentioned .

TV Exterior VHF-UHF Antenas | Tienda de Electronica - TeleEquipo

best regards
Francisco
 

FOX TV

Contributor
#10
Got Plans?

I will have to measure the elements that I made using an original C-2 Antenna. I actually took it apart without breaking it and ATTEMPTED to measure the internal driven element. Actually, since it is a tapered loop, I ended up tracing its dimensions, and using the metal cover from an old and dead DVR recorder I got out of the companies old equipment grave yard..IE The basement to make the driven elements. I have pictures of it, but like Homer Simpson, I can't figure out how to embed a photo, or attatch a file or....any of the neat things that others seem to have figured out how to do. Maybe if i were to just scroll down and look at the entire page, instead of just typing my thoughts in the posting window...Hummm, what an idea !!!

Sorry for the dual post, but I simply got click happy with the back button, and wah-lah, two almost identical posts...Ain't Technology great !!
 

Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#12
Francisco,

It looks like you built a version of a periodic Yagi antenna and honestly, I have no idea why it works for you at all! Take a look at my photo albums here and you will see the Yagis I have built NEVER use connecting wiring or a harness from element-to-element. They are supposed to be "parasitic elements" precisely located so they "influance" each other, contributing to directivity and signal strength gain, and also a reduction of signal reception from unwanted directions (multipath).

If you want to build engineered Yagi antennas, please try this link: Martin E. Meserve - K7MEM - VHF/UHF Yagi Antenna Design It will do all of the math for you.

Jim

PS I have sent you a private mail.
 

scandiskwindows9x

Moderator of DTV Latino
#13
well just tried, i know is not a antenna that can be ok for long use but by now can use it, till purchase a antenna for rooftop

well of anyway i would not do any antenna anymore, i am not good in manual works.
 

scandiskwindows9x

Moderator of DTV Latino
#14
Well, many are wondering why the map dissapeared, well just for security reasons, I had to erase it, just, thought very well and is risky the thing that have done, but well is the picture gone.
 
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MrPogi

Moderator, , Webmaster of Cache Free TV
Staff member
#15
Seriously, If 2 kids can make an antenna, you can, too. (these are lot easier than the one you made!)

YouTube - Making a Gray-Hoverman DTV Antenna with Naomi and Noah

This one is almost as easy:




Video here:
Maker Workshop - DTV Antenna & Steadicam on MAKE: television on Vimeo

PDF: plans for coathanger antenna

I do suggest you put a reflector screen behind them for your location!

BTW, don't use these outdoors, but all you have to do is use 10 gauge copper, some pvc / plastics, or other durable materials instead of wood and "coat hangers", and it will be fine outdoors.
 
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scandiskwindows9x

Moderator of DTV Latino
#16
question, well what antenna would be the best the conventional outdoor one like this

Antena Exterior FA-12 UHF TV DIGITAL | Tienda de Electronica - TeleEquipo | en Santiago

or this one that look like a mini antenna of cell phone for add coverage in metropolitan areas

http://www.casaroyal.cl/productos.aspx

i am confused i think the second one is not that reliable

also yesterday discovered how unreliable is OFDM, was in the house using welding mchines for wel a steel bar was near of the homemade antenna that i did and the image started to get pixellated when the welding machine was working, so the system is not that heavy duty
 
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Fringe Reception

Super Moderator, Chief Content Editor
Staff member
#17
The link to the antenna looks like a "Chinese-wonder" to me. If you want a REAL UHF antenna, I could send you an old-style Channel Master 4221 or a 4228. They appear on e-Bay from time to time as well. I cannot guess the cost to ship one, but it would be a real spank to your wallet. Potentially worth it.

Jim
 

scandiskwindows9x

Moderator of DTV Latino
#18
would have to think and well as here is not really something that be as the best of the best,was watching the website of channel master the past week and well looks the antennas as the best for my case, the antenna that is in the second link, just looks as unreliable i do not know is not as a antenna for even get analogic TV in here, would be as ok for get some wi fi signals but DTV is like weak.

how that antenna would works?

http://cgi.ebay.com/Channel-Master-...020?pt=LH_DefaultDomain_0&hash=item4cf439b4bc

is an exotic type of antenna but look like something as powerful despite the size.
 
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